html,body,#app{
    height: 100%;
    margin: 0;
    padding: 0;
    
    background-image: url(//s1.hdslb.com/bfs/static/stone-free/dyn-home/assets/background.png);
}
.isFixed{
    position: fixed;
    margin-top: 0px;
    z-index: 4;
    width: 100%;
}

